Tubular goods are used in a variety of industrial applications, which may be particularly sensitive to internal defects. For example, a particular tubular good may have internal-external thickness variations, hairline fractures, seams, and various other longitudinally-oriented, transversely-oriented, and obliquely-oriented defects, which may be undetectable by alternative inspection techniques. These defects may arise during the initial manufacturing process, the subsequent processing or transportation, or they may occur as service-induced defects. In many industrial applications, the foregoing defects may lead to environmental damage, bodily injury, equipment damage and downtime, and loss of the associated product, such as hydrocarbon reserves.
Ultrasonic testing has been found to be particularly useful in detecting the foregoing defects, and in certain instances, ultrasonic testing provides the only detection mechanism for such defects. A variety of ultrasonic testing systems currently exist for testing tubular goods following manufacture and other processing stages. Each of these ultrasonic testing systems performs an ultrasonic examination in a helical scanning pattern about the surface of the tubular good. In fluid immersion systems, the tubular good is moved rotationally and longitudinally through a fluid bath, where a number of ultrasonic transducers reside. Although the fluid medium provides relatively low signal degradation from the ultrasonic transducers, these fluid immersion systems are cumbersome and difficult to use in pinpointing defects due to the size and momentum of the tubular goods. In rotating head systems, an assembly of ultrasonic transducers is rotated at high speeds about a tubular good, which is moved longitudinally through the rotating head assembly. Again, the size and momentum of the tubular good complicates the pinpointing of defects within the tubular good.
In other systems, the ultrasonic transducers are mounted in a contoured solid material, such as polystyrene or Lucite, which is moved along the rotating tubular good. In a different application, the ultrasonic transducers may be mounted in a rubber or polystyrene wheel. Both of these systems have a relatively lower sensitivity due to the use of an additional solid interface between the tubular good and the ultrasonic transducers. Moreover, the solids may have defects, such as scratches, which further reduce the ultrasonic sensitivity. These solid-interface systems also have other drawbacks, such as the inability to focus the ultrasonic beams, the relatively narrow inspection width of the rubber wheel system, and the consumability of the polystyrene shoe system.
The foregoing ultrasonic testing systems generally do not test ends of the tubular good, but rather a separate end-testing unit is used to perform an inspection at each end of the tubular good. Special End-Area-Testing units are necessary to complete the testing of the tubular good, because the foregoing ultrasonic testing systems are incapable of traveling fully across the tubular good from end-to-end. Special End-Area inspection units may use ultrasonic means, but more typically employ wet or dry magnetic particle methods. The magnetic particle inspection methods do not provide for a hard copy record of the test, and is less sensitive to internal defects than ultrasonic tests. For example, an ultrasonic testing system having a length of 18 inches is incapable of fully testing the outer 18 inches at each end of the tubular good.
Accordingly, a technique is needed for ultrasonically testing a tubular good from end-to-end using a single ultrasonic testing assembly. A technique is also needed for ultrasonically testing the tubular good through a fluid interface with the tubular good, which is rotated while the ultrasonic testing assembly is moved along the tubular good.